Method and apparatus for performing real-time, in-the-field switching-order simulation for an electric power system

ABSTRACT

One embodiment of the present invention provides a system for performing a real-time, in-the-field switching-sequence simulation for a power system that includes a plurality of switching devices. During operation, the system receives, at a hand-held device, topology information associated with the power system, a set of user-definable rules, and a request to perform an operation on a switching device in the power system. In response to the request, the system identifies the switching device from the plurality of switching devices, obtains instant status information associated with the plurality of switching devices, and runs a simulation based on the topology information, the user-definable rules, the status information, and the identified switch device. The system determines whether the operation is allowed based on an outcome of the simulation.

RELATED APPLICATION

The subject matter of this application is related to the subject matterof the following application:

U.S. Patent Application No. TBD (Attorney Docket No. YTC11-1001US),entitled “METHOD AND SYSTEM FOR PREVENTING MISOPERATION IN AN ELECTRICPOWER SYSTEM,” by inventors Shuctiang Jin, Lingzhi Pang, Liguo Wan,Jiandong Huang, and Hongping Jiang, filed TBD; and

U.S. Patent Application No. TBD (Attorney Docket No. YTC11-1004US),entitled “A HANDHELD DEVICE FOR PREVENTING MISOPERATION IN AN ELECTRICPOWER SYSTEM,” by inventors Shuctiang Jin, Lingzhi Pang, Liguo Wan,Jiandong Huang, and Hongping Jiang, filed TBD;

the disclosures of which are incorporated by reference in their entiretyherein.

BACKGROUND

1. Field

The present disclosure relates generally to management of an electricpower system. More specifically, the present disclosure relates to asystem for performing real-time, in-the-field switching-order simulationin an electric power system.

2. Related Art

In complex electric power plants or transmission substations, wherevarious types of equipment are operating at high voltages, switchingerrors can lead to disastrous outcomes, such as interruptions of power,damages to equipment, and loss of human life. A number of factors cancause switching errors, including equipment failure, faults of thecontrol system, human error, and inadequate interlocking devices.Statistics have shown that most switching errors are caused by humanerror, which can be prevented with proper interlocking design.

Common switching errors include energizing a grounded line, closing aground switch when energized, de-energizing or load dropping using adisconnector instead of a breaker, or entering an energized switchingbay. In order to prevent these switching errors, it is essential toensure that the correct switching sequence is followed by the switchingpersonnel. In addition, the switching personnel must be fully aware ofthe impact of each switching step and have the assurance that the nextstep is proven safe before the actual switching takes place. Thisrequires a simulation system that models the connectivity of asubstation and the interlocking logic among the switching operations.Before operating on a piece of equipment, a worker is required toperform a switching-sequence simulation, which verifies whether thesequence of operations complies with safety rules and regulations. If anoperation step violates a safety rule, the simulation system notifiesthe worker such operation cannot proceed.

Conventional switching-sequence simulation systems rely on humanprogrammers to generate and input logic expressions that describeoperation of the equipment, which can require a huge amount of work fora large-scale, complex power system, and thus is prone to unintendedomissions or typographical errors. In addition, certain complex circuitconfigurations, such as a bridge-circuit configuration, may involvecomplex logic due to interconnections among associated devices, makingit difficult to summarize all possible operating modes.

SUMMARY

One embodiment of the present invention provides a system for performinga real-time, in-the-field switching-sequence simulation for a powersystem that includes a plurality of switching devices. During operation,the system receives, at a hand-held device, topology informationassociated with the power system, a set of user-definable rules, and arequest to perform an operation on a switching device in the powersystem. In response to the request, the system identifies the switchingdevice from the plurality of switching devices, obtains instant statusinformation associated with the plurality of switching devices, and runsa simulation based on the topology information, the user-definablerules, the status information, and the identified switch device. Thesystem determines whether the operation is allowed based on an outcomeof the simulation.

In a variation on this embodiment, the hand-held device is a smart key,which is configured to unlock a lock associated with the switchingdevice, thus facilitating performance of the operation.

In a further variation, identifying the switching device involves usingthe hand-held device to check an RFID associated with the switchingdevice.

In a variation on this embodiment, the plurality of switching devicesincludes at least one electrically operated switching device and onemanually operated switching device.

In a variation on this embodiment, the system updates status of theswitching device after of the operation is performed.

In a variation on this embodiment, the user definable rules areindependent of the power system topology.

In a variation on this embodiment, running the simulation involvesextracting one or more rules associated with the operation andperforming one or more searches that traverse the power system topologybased on the extracted rules.

BRIEF DESCRIPTION OF THE FIGURES

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1A presents a diagram illustrating the process of the “five-step”method, in accordance with an embodiment of the present invention.

FIG. 1B presents a diagram illustrating an exemplary error-preventionprocess, in accordance with an embodiment of the present invention.

FIG. 2 presents a diagram illustrating the architecture of asimulation-and-control system, in accordance with an embodiment of thepresent invention.

FIG. 3 presents a diagram illustrating the architecture of thesimulation module, in accordance with an embodiment of the presentinvention.

FIG. 4A presents a flow chart illustrating the operation process of theswitching-error prevention system, in accordance with an embodiment ofthe present invention.

FIG. 4B presents a flow chart illustrating the process of performing areal-time, in-the-field simulation, in accordance with an embodiment ofthe present invention.

FIG. 5 presents a portion of an exemplary one-line diagram.

FIG. 6 presents a diagram illustrating an exemplary user interface, inaccordance with an embodiment of the present invention.

FIG. 7 presents a diagram illustrating an exemplary computer system forperforming switching-order simulations, in accordance with an embodimentof the present invention.

In the figures, like reference numerals refer to the same figureelements.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the invention, and is provided in the context ofa particular application and its requirements. Various modifications tothe disclosed embodiments will be readily apparent to those skilled inthe art, and the general principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the present invention. Thus, the present invention is notlimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein.

Overview

Embodiments of the present invention provide a system for performing areal-time, in-the field switching-sequence simulation. The systemincludes a server and a handheld device. The server includes a topologyanalyzer and a rule database. The topology analyzer analyzes thetopology of a substation based on the single-line diagram of thesubstation and constructs a node table, which includes statusinformation of each node and the connectivity information among allnodes. The rule database stores a set of predetermined operation rules.Users of the system are allowed to view and edit the operation rulesstored in the rule database. The handheld device receives the node tableand the rules from the server. During operation, a field staff membercarries the handheld device to the field where the switching device islocated. In response to an operation request, the handheld deviceidentifies the switching device associated with the operation andobtains the instant status information of all equipment within the powersystem. Subsequently, the handheld device performs a simulation based onthe identified device, the topology, the rules, and the instant statusinformation to determine whether the requested operation is allowable.

Smart-Interlock System

To prevent possible switching errors involved in a switching operation,in embodiments of the present invention, a transmission substation or aswitching/dispatching center implements a smart-interlock system (SIS),which combines the reliability of mechanical interlocking and theflexibility of electrical interlocking The SIS includes a centralsimulation-and-control system, a smart key, and various types of locksassociated with field equipment. During operation, the SIS uses a“five-step” method to ensure switching safety. The five steps forperforming safe switching include: a simulation step, a switching-ordertransmission step, a device ID verification step, anoperation-permission revalidation step, and a switching-completion step.FIG. 1A presents a diagram illustrating the process of the “five-step”error-prevention method, in accordance with an embodiment of the presentinvention.

Before an actual switching takes place, a simulation is performed toensure that the proposed switching sequence is safe (operation 108).Note that this simulation can be performed by a simulation-and-controlsystem 102 located in the substation control room. Theswitching-sequence simulation outputs a switching order that specifieswhich equipment is to be operated on and the order of the operations.Subsequently, the switching order is transmitted to a smart key 104during the switching-order transmission step (operation 110). Smart key104 is a handheld device that is capable of communicating, using variouswireless communication protocols (such as ZigBee or CDMA), with thesimulation-and-control system. In addition, smart key 104 is capable ofinteracting and unlocking various locks, such as a lock 106, associatedwith the field equipment. Note that the locks are attached to theequipment, and operations on the equipment require unlocking these locksusing smart key 104. Smart key 104 can be carried by a person designatedto perform the switching operation in the field, where the equipment islocated. For example, before that field person pushes the handle of aknife switch, he first needs to unlock a lock that fixes the handle toits position. Or, before the field person enters a breaker bay toperform switching operations, he needs to first unlock the door of thebreaker bay. During the device-ID verification step, the field personuses the smart key to verify that the equipment to be operated on is theidentified equipment by checking an identifier associated with theequipment (operation 112). Such equipment identifier can be implementedby a lock identifier. For example, a lock (such as a padlock) attachedto the equipment can be embedded with a radio frequency identification(RFID) tag, and an RFID detector included in the smart key can read thisRFID in order to verify the identity of the lock, and thus the identityof the equipment. Optionally, subsequent to verifying the ID of theequipment to be operated on, the field person can further revalidate theoperation by sending the operation request for the current equipmentback to the simulation-and-control system via the smart key (operation114) and receiving a validation result from the simulation-and- controlsystem (operation 116). Subsequent to receiving the revalidation result,the field person uses the smart key to unlock the lock (either anelectronic lock or a mechanical lock) and performs the actual switching(operation 118). For example, the field person may need to unlock apadlock in order to move the swing handle of a disconnect switch; or hemay need to unlock a lock on the door of a cabinet in order to operateon equipment inside the cabinet. Note that the operation can be a manualoperation that requires the field person to physically move a switchhandle or an automated, electrically operated operation. Aftercompletion of the switching operation, smart key 104 updates the statusof the equipment by transmitting its current status back tosimulation-and-control system 102 (operation 120).

In one embodiment, in addition to obtaining the simulated switchingorder, smart key 104 performs an additional operation-verification step,which involves running a real-time, in-the-field switching-ordersimulation. FIG. 1B presents a diagram illustrating an exemplaryerror-prevention process, in accordance with an embodiment of thepresent invention. In FIG. 1B, the operations performed bysimulation-and-control system 102 and smart key 104 are similar to theoperations shown in FIG. 1A. More specifically, simulation-and-controlsystem 102 performs the switching-sequence simulation (operation 108)and transmits the switching order to smart key 104 (operation 110).Smart key 104 verifies the equipment to be operated on by verifying theID of lock 106 (operation 112). Optionally, smart key 104 revalidatesthe switching operation by communicating with simulation-and-controlsystem 102 (operations 114 and 116). Unlike the process shown in FIG.1A, in FIG. 1B, prior to unlocking lock 106, smart key 104 performs aswitching-sequence simulation (operation 122). Because theswitching-sequence simulation is performed by smart key 104 right beforethe switching operation, this simulation is a real-time simulation.Performing a real-time switching-sequence simulation can beadvantageous, especially in the scenario where the status of certainequipment has changed after simulation-and-control system 102 performsthe initial switching-sequence simulation. Such a status change mayresult in the previously generated switching order being flawed. Forexample, the previously run simulation may indicate that a closingoperation on a knife switch is a safe operation. However, before thefield staff member performs such an operation, a circuit breaker coupledto the knife switch may change its status from open to closed, thusrendering the knife switch closing operation unsafe. Hence, a real-time,in-the-field switching-sequence simulation is needed to preventexecution of the unsafe operation. In one embodiment, smart key 104receives real-time status information of certain automated devices froma supervisory control and data acquisition (SCADA) system coupled tothose devices. In a further embodiment, a server (such as a server atwhich simulation-and-control system 102 resides) relays the SCADA datato smart key 104. Note that real-time status information for manuallyoperated devices, such as fence doors and temporary ground wires, arecollected and reported by smart keys.

Simulation-and-Control System

The simulation-and-control system is an essential part of the SIS. Ituses the one-line diagram of a substation to obtain the circuitrytopology; collects current equipment status; collects and modelsswitching interlock logic and rules; and simulates the switchingsequence based on the circuitry topology, current equipment status, andswitching interlock logic and rules. FIG. 2 presents a diagramillustrating the architecture of a simulation-and-control system, inaccordance with an embodiment of the present invention.Simulation-and-control system 200 includes a simulation module 202, astate machine 204, a user interface 206, and a control module 208.

During operation, state machine 204 receives the current equipmentstatus information for a substation, including status information ofautomated devices collected by a supervisory control and dataacquisition (SCADA) system and status information of manually operateddevices collected by smart keys, which performs the remote operationsurveillance for the SIS, and sends the equipment status information tosimulation module 202. Simulation module 202 performs switching sequencesimulation using current equipment status, topology informationextracted from the substation one-line diagram, and the switchinginterlock logic and rules. The detailed structure of simulation module202 is shown in FIG. 3. Based on the simulation result, simulationmodule 202 generates a switching order. User interface 206 displayspossible error information and system warnings, and communicates withthe smart key. In addition, control module 208 issues control commandsto the SCADA system to realize the remote control operations.

Simulation-and-control system 200 can reside on any type of computersystem based on microprocessors, such as a standalone mainframe computeror a cluster of computer servers. In one embodiment,simulation-and-control system 200 resides on a handheld device, such asa smart key, to enable real-time, in-the-field simulation. Note that dueto the input/output or computation constraints of a handheld device, itis possible to have only a portion of simulation-and-control system 200(such as simulation module 202) to resides on the handheld device, whileother modules of simulation-and-control system 200 remain on acentralized server.

FIG. 3 presents a diagram illustrating the architecture of thesimulation module, in accordance with an embodiment of the presentinvention. Simulation module 300 includes an equipment analyzer 302, astatus database 304, a topology analyzer 306, a rule database 308, and asimulation engine 310.

Equipment analyzer 302 analyzes the structural components of each pieceof equipment associated with the switching operation, and decomposes apiece of complex equipment into a number of basic components, such ascircuit breakers, disconnects, and ground disconnects, that fulfill theelectrical functionality of the complex equipment. For example, athree-position knife switch is decomposed to two basic components: aknife switch and a ground knife switch. The three switching positionscorrespond to different switching positions of the knife switch and theground knife switch. Note that after a piece of complex equipment isdecomposed into multiple basic components, connections to other externalequipment are mapped onto corresponding ends on the basic components.The output of equipment analyzer 302, including the status of the basiccomponents and their connection information, is stored in statusdatabase 304. Note that the status information of the components can beupdated by the smart key. In one embodiment, after each operation, thesmart key updates the status of the equipment being operated on. Such anarrangement makes it possible for the system to maintain real-timestatus information of all equipment, including manually operatedequipment in the field, such as a manual switch or a locked door for aswitching bay.

Topology analyzer 306 analyzes the topology of a substation based on theone-line diagram and the decomposition outcome of each piece of complexequipment. In one embodiment, topology analyzer 306 constructs a nodetable, which includes the status of the nodes and connection informationamong the nodes. Note that each node in the node table corresponds to atopology node extracted from the one-line diagram of the substation. Inone embodiment, a topology node corresponds to a crossing point on theone-line diagram, which can include one or more equipment endpoints.Note that a single topology node may be associated with multipleendpoints, whereas a particular endpoint can only be associated with asingle topology node.

Rule database 308 stores switching interlock logic and rules, which canbe either programmed ahead of time by the manufacturer of the SIS ordefined by the user of the SIS. For example, to prevent operations on aloaded knife switch, rule database 308 stores a rule stating that nooperation (either opening or closing) is allowed on a knife switch whenthe knife switch is coupled to a closed circuit breaker. Note that theserules generally describe allowed or disallowed operations of basiccomponents, regardless of their relative locations in the systemtopology. The independent relationship between rule database 308 and thesystem topology provides scalability for the SIS. When the substationscales up, such as with the addition of new equipment, instead ofreprogramming the entire simulation software, one only needs to inputthe updated one-line diagram into topology analyzer 306. Moreover, whensafety rules and regulations are changed, only rule database 308 needsto be updated. Such updating can be made by users of the SIS. In oneembodiment, the switching interlock logic and rules are stored in atable, and the user is allowed to add, delete, or make changes to thetable entries. In a further embodiment, an entry in rule database 308includes three components: equipment type, operation type, andexpression of the rule specific to the equipment and the operation. Theequipment type component specifies the type of equipment (such asbreakers, knife switches, and ground wires) that this rule is appliedto; the operation type specifies which operation (such as opening orclosing) that this rule is applied to; and expression of the rule is alogic expression describing the error-prevention rule. Such a logicexpression is specific to the type of equipment and the type ofoperation, and remains unrelated to any specific piece of equipmentwithin the system. In the aforementioned example, a corresponding entryfor closing a knife switch in rule database 308 can be expressed as:KNIFE SWITCH, CLOSING: KNIFE SWITCH UNLOADED. Such a rule is applied toall knife switches in the system, including a knife switch that wasincluded in and decomposed from a piece of complex equipment.

Once the system receives an operation request on a piece of equipment,simulation engine 310 performs a simulation to determine whether therequested operation is allowed based on the topology node tableconstructed by topology analyzer 306, equipment status informationextracted from status database 304, and operation rules extracted fromrule database 308.

FIG. 4A presents a flow chart illustrating the operation process of theswitching-error prevention system, in accordance with an embodiment ofthe present invention. Prior to receiving a request to perform aswitching operation, the system goes through an initialization process,which includes receiving the one-line diagram of a power plant or asubstation (operation 402), extracting topology information from theone-line diagram (operation 404), and constructing a topology node table(operation 406). Note that this initialization process can be performedwhen the power system is brought online, or when the power systemexperiences equipment update. The system waits for a request for anoperation on a particular piece of equipment, such as a request forclosing a knife switch (operation 408). Upon receiving such a request,the system extracts a rule associated with the equipment and theoperation from the rule database (operation 410). Based on the rule, thesystem derives a number of operating conditions complying with the rule(operation 412). For example, a rule associated with closing a knifeswitch states that such an operation requires that the knife switch beunloaded, and the operating conditions that satisfy this rule include:all circuit breakers coupled to the knife switch being open, and atleast one side of the knife switch being unloaded.

Based on the derived operating conditions, the system defines a searchthat starts from one or more endpoints of the equipment and traversesthe electrical connectivity topology (operation 414). The targets andboundary of the search are defined by the operating conditions. Forexample, to determine whether the condition of all coupled circuitbreakers being open is met, the system first defines a search boundary,which includes circuit breakers and open knife switches. In other words,a search originating from a node and traversing the topology will cometo a stop once a circuit breaker or a knife switch is met. The searchtarget is a closed circuit breaker. Note that if the search returns aclosed circuit breaker, it indicate a violation of the operationcondition. Similarly, to determine whether the condition of at least oneend of the knife switch being unloaded is met, the system first definesa search boundary, which includes open circuit breakers and open knifeswitch. The search targets include loaded devices or a power supplies.The system then obtains the current status of the equipment within thetopology (operation 416). In one embodiment, the system interfaces withan EMS (Energy Management System)/SCADA system to obtain the currentoperational status (such as positions of a switch) of the equipment. Ina further embodiment, the current status of the equipment can beobtained by the smart key.

Subsequently, the system performs the search that traverses the topology(operation 418). The search starts from one or more endpoints of theequipment. In the example of the knife switch, the search starts fromboth ends of the knife switch. The search traverses the electricalconnectivity topology, and collects equipment associated with theoperating conditions. For example, using the operating condition thatall circuit breakers coupled to the knife switch are open, the systemdefines a search boundary that includes open circuit breakers and openknife switches, and the search targets include loaded devices and powersupplies. Based on the search result and the current equipment status,the system determines whether the operating conditions are met(operation 420). If the operating conditions are met, the systemindicates to the user that the operation is allowed (operation 422).Otherwise, the system displays error information to the user (operation424). In one embodiment, the error information includes the searchresult indicating the violated operating condition. In the example ofthe knife switch, the search may find a coupled circuit breaker having acurrent status of being closed, and indicate to the user that operationson the knife switch are prohibited due to the status of that particularcircuit breaker. Note that such information can be used by the user tocorrect the situation. In the above example, the error informationindicates that operations on the knife switch are prohibited because acoupled circuit breaker is closed. The user can then attempt to open thecircuit breaker first in order to operate on the knife switch. In afurther embodiment, if the violated operating condition is not acritical condition (such as a one that does not violate a safety rule),the error message may include an option that allows the user to overridethe decision made by the system. Based on the user's input, the systemmay indicate that such an operation is allowed or not.

In one embodiment, to ensure that the requested switching operationremains safe, the system performs the switching-sequence simulation on ahandheld device right before a field staff member performs the switchingoperation. For example, in order to perform the switching operation, afield staff member needs to use a smart key to unlock a lock attached tothe switching equipment; and before unlocks the lock, the smart key isconfigured to obtain the instant equipment status and run theswitching-sequence simulation using the newly obtained equipment status.In one embodiment, the smart key is unable to unlock the lock unless thesimulation result indicates the switching operation is allowed. Becausethis simulation is run real-time, it ensures the validity of thesimulation result.

Since it is less likely for the system topology or the interlock logicand rules to make sudden changes, there is no need for the smart key toperform topology analysis or to update its rule database withuser-defined rules. Instead, the smart key can receive topologyinformation (such as the node table) and the rules from a remote server,which performs the topology analysis and rule update. FIG. 4B presents aflow chart illustrating the process of performing a real-time,in-the-field simulation, in accordance with an embodiment of the presentinvention.

Prior to performing the real-time, in the field operation, the handhelddevice or the smart key receives the topology node table from the SISserver (operation 430). In addition, the smart key also receives theuser-definable rules stored in the rule database from the SIS server(operation 432). Note that to ensure that the smart key has the updatedversion of the topology and rules, in one embodiment, each time theserver updates the topology or rules, the server will notify the smartkey to re-download the topology node table and rules. Subsequently, thesmart key waits to receive a request for an operation on a piece ofequipment (operation 434). In one embodiment, the smart key receives theoperation request directly from a user. For example, a holder of thesmart key can manually input a command on the smart key. In a furtherexample, the smart key receives the operation request from the SISserver. For example, a control staff member issues an operation requestat the SIS server, which approves and forwards the request to the smartkey.

Before the switching operation is performed, a field staff membercarries the smart key to the field and uses the smart key to engage alock associated with the switching operation (operation 436). Forexample, before swinging the handle of a knife switch, the field staffmember needs to unlock a lock attached to the handle by inserting thekey head of the smart key into the lock. In one embodiment, when thesmart key engages the lock, it verifies the lock identifier (operation438). If the lock-ID has been verified, the smart key obtains theinstant equipment status of the power system (operation 440). In oneembodiment, the smart key obtains the instant equipment statusinformation from a SCADA system that monitors equipment status for thepower system. In a further embodiment, the smart key obtains the instantequipment status from the SIS server. Subsequently, the smart key runs asimulation based on the operation request and the instant equipmentstatus (operation 442). In one embodiment, the simulation operation issimilar to operations 410-420 shown in FIG. 4A, which involve performingone or more searches that traverse the topology. In a furtherembodiment, the simulation can be any other type of error-preventionsimulation which may or may not involve a search based on user definablerules. Based on the simulation outcome, the system determines whetherthe operation is allowed (operation 444). If so, the smart key is enableto unlock the lock (operation 446). Immediately after the correspondinglock is unlocked, the field staff member performs the switchingoperation. If the operation is not allowed, the smart key displays errorinformation to the user (operation 448). Subsequent to the switchingoperation, the smart key updates the status of this particular equipment(operation 450).

Note that it is advantageous to have the smart key to record and updatethe equipment status. Conventional power systems often rely on a SCADAsystem to monitor the status of the equipment. However, the SCADA systemcan only monitor and collect status information from equipment that isautomatically operated or installed with sensors. In a transmissionsubstation, many switching devices are manually operated and installingsensors on all manual equipment can be unpractical. Hence, the SCADAsystem alone cannot provide all updated statuses for all equipment. Forexample, the connection status of a temporary ground wire may not beavailable to the SCADA system. On the other hand, because connecting ordisconnecting the temporary ground wire involves unlocking one or morelocks associated with the ground wire, the connection status of theground wire can be obtained by the smart key. By updating the status ofa device each time after an operation has been performed on the device,the smart key is able to track the status of all equipment in the powersystem, including manually operated equipment, such as a temporaryground wire or a knife switch.

An Operation Example

FIG. 5 presents a portion of an exemplary one-line diagram. One-linediagram 500 includes a breaker 502, two knife switches 504 and 506, andtwo ground switches 508 and 510. During initialization, theswitching-error prevention system extracts connectivity topologyinformation from one-line diagram 500 and constructs a node table. Thenode table includes a number of topology nodes (such as nodes 512 and514) and connectivity information associated with the switching devices.For example, one endpoint of ground switch 510 is coupled to an endpointof knife switch 506 and an endpoint of breaker 502 at node 514.

Upon receiving an operation request to close ground switch 510, thesystem extracts a rule stating that before the closing operation cantake place on a ground switch, the ground switch needs to be isolatedfrom other equipment. Based on the rule, the system determines that thecorresponding operating condition is that all knife switches coupled toground switch 510 remain open. Based on the operating condition, thesystem defines a search for a closed knife switch coupled to groundswitch 510. This search starts from the ungrounded end of ground switch510, and traverses the entire topology. The search boundary includesknife switches and the search targets include closed knife switches. Anempty search result indicates that ground switch 510 is isolated fromother equipment. Consequently, the system determines that the operatingcondition is met, and the operation of closing ground switch 510 isallowed. Note that if a knife switch coupled to ground switch 510, suchas knife switch 506, is closed, the system will determine that therequested closing operation of ground switch 510 is prohibited, anddisplay an error message to the user. The message can notify the userthat the requested operation is prohibited because knife switch 506 isclosed.

User Interface

FIG. 6 presents a diagram illustrating an exemplary user interface, inaccordance with an embodiment of the present invention. In oneembodiment, the switching-error prevention system includes a graphicuser interface (GUI) that enables a user to interact with theswitching-error prevention system.

The GUI can be presented to the user on various types of displaymechanisms, such as a standard computer display or a touch-screendisplay. In FIG. 6, GUI 600 displays the one-line diagram of asubstation. In one embodiment, the displayed one-line diagram alsodisplays the current status of the equipment, such as a switch beingopen or closed. A user can request an operation on a piece of switchingequipment by pointing and clicking an icon on the diagram correspondingto the equipment. The simulation result in response to the operationrequest is presented to the user via GUI 600.

In one embodiment of the present invention, GUI 600 can switch the viewfrom the one-line diagram shown in FIG. 6 to a view that displays atable associated with the rule database. The table view of the ruledatabase enables the user to make changes to the rule database byadding, deleting, and modifying entries in the table.

Computer System

FIG. 7 presents a diagram illustrating an exemplary computer system forperforming switching-order simulations, in accordance with an embodimentof the present invention. In one embodiment, a computer andcommunication system 700 includes a processor 702, a memory 704, and astorage device 706. Storage device 706 stores a switching-ordersimulation application 708, as well as other applications, such asapplications 710 and 712. During operation, switching-order simulationapplication 708 is loaded from storage device 706 into memory 704 andthen executed by processor 702. While executing the program, processor702 performs the aforementioned functions. Computer and communicationsystem 700 is coupled to an optional display 714, keyboard 716, andpointing device 718. The display, keyboard, and pointing device canfacilitate switching-order simulation.

The foregoing descriptions of embodiments of the present invention havebeen presented only for purposes of illustration and description. Theyare not intended to be exhaustive or to limit this disclosure.Accordingly, many modifications and variations will be apparent topractitioners skilled in the art. The scope of the present invention isdefined by the appended claims.

What is claimed is:
 1. A method for performing a real-time, in-the-fieldswitching-sequence simulation for a power system that includes aplurality of switching devices, comprising: receiving, at a handhelddevice, topology information associated with the power system; receivinga set of user-definable rules; receiving a request to perform anoperation on a switching device in the power system; in response to therequest, identifying the switching device from the plurality ofswitching devices; obtaining instant status information associated withthe plurality of switching devices; and running a simulation, at thehand-held device, based on the topology information, the user-definablerules, the status information, and the identified switch device; anddetermining whether the operation is allowed based on an outcome of thesimulation.
 2. The method of claim 1, wherein the handheld device is asmart key, and wherein the method further comprises enabling the smartkey to unlock a lock associated with the switching device, thusfacilitating performance of the operation.
 3. The method of claim 2,wherein identifying the switching device involves using the handhelddevice to check an RFID associated with the switching device.
 4. Themethod of claim 1, wherein the plurality of switching devices includesat least one electrically operated switching device and one manuallyoperated switching device.
 5. The method of claim 1, further comprisingupdating status of the switching device after the operation isperformed.
 6. The method of claim 1, wherein the user-definable rulesare independent of the power system topology.
 7. The method of claim 1,wherein running the simulation involves: extracting one or more rulesassociated with the operation; and performing one or more searches thattraverse the power system topology based on the extracted rules.
 8. Anon-transitory computer-readable storage medium storing instructionsthat when executed by a computer cause the computer to perform a methodfor performing a real-time, in-the-field switching- sequence simulationfor a power system that includes a plurality of switching devices,wherein the method comprises: receiving, at a handheld device, topologyinformation associated with the power system; receiving a set ofuser-definable rules; receiving a request to perform an operation on aswitching device in the power system; in response to the request,identifying the switching device from the plurality of switchingdevices; obtaining instant status information associated with theplurality of switching devices; and running a simulation, at thehand-held device, based on the topology information, the user-definablerules, the status information, and the identified switch device; anddetermining whether the operation is allowed based on an outcome of thesimulation.
 9. The computer-readable storage medium of claim 8, whereinthe handheld device is a smart key, and wherein the method furthercomprises enabling the smart key to unlock a lock associated with theswitching device, thus facilitating performance of the operation. 10.The computer-readable storage medium of claim 9, wherein identifying theswitching device involves using the handheld device to check an RFIDassociated with the switching device.
 11. The computer-readable storagemedium of claim 8, wherein the plurality of switching devices includesat least one electrically operated switching device and one manuallyoperated switching device.
 12. The computer-readable storage medium ofclaim 8, wherein the method further comprises updating status of theswitching device after the operation is performed.
 13. Thecomputer-readable storage medium of claim 8, wherein the user-definablerules are independent of the power system topology.
 14. Thecomputer-readable storage medium of claim 8, wherein running thesimulation involves: extracting one or more rules associated with theoperation; and performing one or more searches that traverse the powersystem topology based on the extracted rules.
 15. A handheld device forperforming a real-time, in-the-field switching-sequence simulation for apower system that includes a plurality of switching devices, comprising:a memory, comprising: a topology node table configured to store topologyinformation associated with the power system; and a rule databaseconfigured to store a set of user-definable rules; a receiving mechanismconfigured to receive a request to perform an operation on a switchingdevice in the power system; an identifying mechanism configured toidentify the switching device from the plurality of devices; astatus-obtaining mechanism configured to obtain instant statusinformation associated with the plurality of switching devices; asimulation mechanism configured to run a simulation based on thetopology information, the user-definable rules, the instant statusinformation, and the identified device; and a determination mechanismconfigured to determine whether the operation is allowed based on anoutcome of the simulation.
 16. The hand-held device of claim 15, furthercomprising a key head configured to unlock a lock associated with theswitching device, thus facilitating performance of the operation. 17.The hand-held device of claim 16, wherein the identifying mechanismidentifies the switching device by checking an RFID associated with theswitching device.
 18. The hand-held device of claim 15, wherein theplurality of switching devices include at least one electricallyoperated switching device and one manually operated switching device.19. The hand-held device of claim 15, further comprising an updatemechanism configured to update status of the switching device after ofthe operation is performed.
 20. The hand-held device of claim 15,wherein the user definable rules are independent of the power systemtopology.
 21. The hand-held device of claim 15, wherein while runningthe simulation, the simulation mechanism is configured to: extract oneor more rules associated with the operation; and perform one or moresearches that traverse the power system topology based on the extractedrules.